International aid non-governmental organisations (IANGOs) are expected by the public and government institutions funding them to focus upon maximising effectiveness for the delivery of aid and in the process adopt ethical procurement (EP) practices. Concerns have been voiced by governments and media regarding the perceived lack of coordination between IANGOs. The motivation for this thesis stems from a societal and personal evaluation of the need for ethical behaviour in the procurement of goods and services for international aid and is supported by a willingness by IANGOs to explore the potential for conducting procurement practices in their supply networks in an ethical manner. To address these issues this research aims to explore ethical procurement strategies for IANGOs in humanitarian supply chains. To achieve these aims our methodological approach is qualitative, which means that it studies the subjects in their natural environments, and seeks to understand phenomena by understanding the meanings given to them by actors. We undertook a multiple case study approach and conducted in-depth interviews with senior logistics and purchasing managers in IANGO organisations, together with a survey of IANGO suppliers. Our contribution to EP strategies for IANGOs at the strategic level is to develop a conceptual framework for collaborative ethical procurement due diligence (CEPDD) between IANGOs in HSCs. At the tactical level we identify inhibitors and enables to CEPDD between IANGOs, their suppliers’ networks and donors. At the operational level we develop a risk-rating framework which provides IANGOs with a tool to establish a collaborative procurement code of conduct (COC) ethics system which can be used to assess ethical risks in HSCs. Our findings demonstrate SC co-opetition strategies are being enacted by IANGOs to explore the formulation of CEPDD. We establish there are concerns surrounding ethical risk in HSCs that differ from CSCs in relation to IANGO relationships with donors, and supplier networks. We apply our risk rating framework to highlight inhibitors to CEPDD throughout IANGO supplier networks and donor relations, and in doing so we determine that apart from the actions of a lead IANGO, ethical procurement due diligence is not instigated in a formalised manner. Tactically our risk-rating framework is of practical importance as it allows IANGOs to access the relevant information concerning inhibitors and enablers in order to evaluate CEPDD ideas and schemes, and to make informed decisions towards participation. These factors facilitate initiatives by directing efforts towards issues of concern and shifting focus towards the critical problem areas which need to be addressed. Operationally it provides a guide in horizontal cooperation considerations in CEPDD by acting as a basis of decision choices for the construction of a framework of COCs between IANGOs.